On Fri, Oct 21, 2022 at 08:22:41PM +0300, Ville Syrjälä wrote: > On Mon, Aug 22, 2022 at 01:18:22PM +0200, Peter Zijlstra wrote: > > +#ifdef CONFIG_LOCKDEP > > + /* > > + * It's dangerous to freeze with locks held; there be dragons there. > > + */ > > + if (!(state & __TASK_FREEZABLE_UNSAFE)) > > + WARN_ON_ONCE(debug_locks && p->lockdep_depth); > > +#endif > > We now seem to be hitting this sporadically in the intel gfx CI. > > I've spotted it on two machines so far: > https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_12270/shard-tglb7/igt@gem_ctx_isolation@preservation-s3@xxxxxxxxx > https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_109950v1/shard-snb5/igt@kms_flip@flip-vs-suspend-interruptible@xxxxxxxxxxx Sadly no luck in reproducing this locally so far. In the meantime I added the following patch into our topic/core-for-CI branch in the hopes of CI stumbling on it again and dumping a bit more data: --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -125,8 +125,16 @@ static int __set_task_frozen(struct task_struct *p, void *arg) /* * It's dangerous to freeze with locks held; there be dragons there. */ - if (!(state & __TASK_FREEZABLE_UNSAFE)) - WARN_ON_ONCE(debug_locks && p->lockdep_depth); + if (!(state & __TASK_FREEZABLE_UNSAFE)) { + static bool warned = false; + + if (!warned && debug_locks && p->lockdep_depth) { + debug_show_held_locks(p); + WARN(1, "%s/%d holding locks while freezing\n", + p->comm, task_pid_nr(p)); + warned = true; + } + } #endif WRITE_ONCE(p->__state, TASK_FROZEN); -- 2.37.4 -- Ville Syrjälä Intel
